As the guy responded when asked why he took off his clothes and jumped into a bed of cactus, "it just seemed like a good idea at the time."
I started at 18, as soon as I got far enough from home to eliminate the flak that would otherwise have been incurred. I had no plan other than to complete the rating, and no idea it would ever be more than a hobby. Having decided against going to Annapolis (10-year commitment for pilots, too tall for jets, engineering only, no girls) the PPL seemed like a logical way to fly something as PIC and keep the door open in the event some aviation-related opportunity arose.
Many more opportunities than I dreamed of obviously showed up from time to time. All were enjoyable for some period of time, all added to the bucket of experience.
I'm now back where I started, flying an old Cessna taildragger like the one in which I took the first lessons, but a respectable X/C ride for the few extended trips that come up from time to time, while 90% of the use is purely social and within a hundred miles of home. Every time I think about recurrent training to fly the turboprops and jets, I close my eyes and sit real still until the urge passes. So far, so good.